This invention relates to lubricant metering assemblies, and more particularly, to a lubricant metering assembly for the continuous supply at a constant rate of flow of a lubricant to a bearing assembly or the like, of a machine or equipment requiring lubrication.
In U.S. Pat. No. 3,498,413 to Krieger, there is disclosed a grease cup assembly comprised of a cup formed of a transparent material positioned within a housing attached to a machine assembly requiring lubrication. A piston and a spring are disposed within the cup to force a lubricant to the machine assembly. A headed valve stem is affixed to the piston and is caused to move within an outwardly tapered flow channel formed within the housing between supply orifices therein and the machine assembly. When the cup is filled to capacity, the tapered head portion seals the orifices and locks the supply orifices in an inoperative position since the piston is unable to move downwardly without effecting the flow of grease therein which is prevented by the closure of the supply orifices by the headed portion of the valve stem. Additionally, fluid control is only initially effected when the combined cross-sectional area of the supply orifices is greater than the cross-sectional area about the annular orifice formed by the configuration of the taper channel with regard to the circumference of the headed portion of the valve stem (on a plane perpendicular to the axis of the stem). Once the headed portion of the valve stem reaches a point where the cross-sectional area of such annular orifice is greater than the combined cross-sectional area of the supply orifices, the flow of lubricant is limited by the restriction of the supply orifices, and since the cross-sectional area of the supply orifices is fixed, there is no compensation for decreasing compressional force of the spring. Additionally, a significant amount of the lubricant capacity of the grease cup assembly is disposed in an annular cavity within the housing and is not expelled by the spring loaded piston. The static segments of the grease volume tends to cake and solidify as the oil content decreases as a result of oil and filler separation thereby resulting in eventual malfunctioning thereof unless the grease cup is periodically disassembled and the caked portion manually removed. Such manual handling requires equipment shut-down as well as presents undesired material handling problems. Further, in order to permit the disassembly of the grease cup for cleaning procedures, it is necessary to remove the grease cup from the associated equipment.